With the significant advances made in the area of genomics, genetic regulators related to plant stress tolerance have been identified, which may have the potential to be utilized in crop improvement through genetic engineering. One example of such a genetic regulator is microRNA (miRNA). MicroRNAs are a class of noncoding small RNAs which originate from pri-miRNA transcripts that are encoded by miRNA genes. The pri-miRNA transcripts are processed into smaller 19-24 nucleotide RNAs, which can regulate gene expression, for example, through silencing reactions by translational inhibition or cleavage.
MiR396 is an evolutionally conserved miRNA family which is involved in both flowering development and abiotic stress responses. It contains two family members (miR396a-b) in Arabidopsis, and six family members (miR396a-f) in rice. Its targets are genes encoding for growth-regulating factor (GRF), which are transcription factors involved in plant growth and development.
Flowering is a crucial phase to determine the plant reproduction success. Optimal flowering time provides favorable environmental conditions for seed development. Many crop species require prolonged exposure to cold (e.g., winter cold) or vernalization to promote their vegetative-to-reproductive stage transition. Vernalization largely limits crop growth region as well as flowering time due to varied winter temperature from place to place and from year to year. In this context, it is highly valuable to develop new strategies to control flowering, including breaking the vernalization requirement.
The present invention overcomes previous shortcomings in the art by providing methods and compositions for transgenic plants with increased cold tolerance and the ability to flower by bypassing vernalization as well as impaired pollen fertility.